Concept of intermediate mixing of slurries in long pipelines

ABSTRACT

In the transmission of solids as a slurry through a pipeline, it is desirable to maintain a uniform slurry concentration, and this the present invention achieves.

United States Patent 1191 Aude June 28, 1974 [54] CONCEPT OF INTERMEDIATE MIXING ()F 2,672,371 3/1954 Jones 302/14 SLU R S IN ON PIPELINES 2,672,372, 3/1954 Jones et a1. 302/14 2,835,536 5/1958 Christi1le..... 302/14 [75] Inventor: Thomas C. Aude, Moraga, Cahf. 2 3 0 7 5 4 959 Regan et 81, 302 14 3,517,969 6/1970 Wicks 1 302/66 [73] Asslgnee' g t g' 'g corporat'on 3,547,497 12/1970 Bolger 302/14 x "mascot 3,582,143 6/1971 Dimopoulos 302/66 x [22 Fil J 15 1973 3,690,730 9/1972 Sakata et al. 302/42 X [21] APPI'NO': 323449 Primary ExaminerEvon C. B1unk Assistant Examiner-W. Scott Carson [52] US. Cl. 302/66, '302/14 Attorney, Agen 0r FirmR0bert H. Eckhoff [51] Int. Cl. B65g 53/30 [58] Field of Search 302/ 14-16, 7 ACT In the transm1ss1on of sohds as a slurry through 21 mm- [5 References Cited line, it is desirable to maintain a uniform slurry con- UNITED STATES PATENTS centration, and this the present invention achieves.

1,541,) 3 Claims, No Drawings 03 6/1925 Crites 302/42 X CONCEPT OF INTERMEDIATE MIXING OF SLURRIES IN LONG PIPELINES BACKGROUND OF THE INVENTION Because of operating errors, the slurry concentration entering the pipeline can vary. 'When the entering slurry is of a low solid concentration, a deteriorating situation develops wherein a low concentration slurry segment dilutes the slurry preceding it, causing the coarser solids to settle out, slide back in the pipeline and be accumulated in the following slurry. As the process continues, the slurry becomes of increasing solid concentration, setting up a so-called concentration wave resulting in non-uniform slurry delivery and, on occasion, actually plugging the pipeline. Once the process is established, it continues creating a longer and longer slug of very thick slurry of segregated size particles. On occasion, this thick slurry results in great difficulty in restarting the flow of slurryin the pipeline if it has been forced to shutdown. 1

SUMMARY OF THE INVENTION It is in general the broad object of the invention to remove the so-called concentration waves from long slurry pipelines so that they will not cause operating upsets such as non-uniform slurry delivery and even, on occasion, plugging of the pipeline.

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with this invention, I provide one or more agitated slurry tanks at intermediate points'in the pipeline. Each tank is of sufficient capacity to fully remix the length of slurry that has been affected by the concentration wave. Experience has shown that a concentration wave travelling approximately 250 miles will grow to a length of approximately I hours pumping time in the pipeline. I therefore provide a tank at the 250 mile point or at the nearest pumping station to that point having a capacity of approximately 2 hours of the system flow so that the slurry can be remixed to uniform concentration before further transit down the pipeline. Thus, I provide instrumentation at the upstream pump station to measure the concentration of the passing slurry. When this instrumentation detects a concentration wave, it initiates the operation of the remixing tank at the next downstream station.

In the event it becomes necessary to rework the slurry to appropriate consistency, it is necessary to pump water into the line to maintain the continuous flow of the slurry present in the line beyond the tank. As a specific example of the practice of the invention, in a pipeline 30 inches in diameter and having-an overall length of 1,000 miles, pumping stations were provided approximately every 80 miles along the line. The

the pumping system so that the slurry continuously enters and leaves each tank; thus each tank acts as a two hour surge in the system thereby remixing anyconcentration upsets that are travelling through the system.

In place of utilizing a tank, one can utilize a suitably lined pond. A pond can be provided at less capital expense than tankage but it may be slightly more expensive to rework the slurry because one has to withdraw the solids from the pond by means of a dredge-like equipment and reform the slurry.

I claim:

l. A method of operating a piepline to convey a slurry of comminuted solids in liquid and to remix slugs of slurry flowing through the pipeline in which heavier particles in a slug of slurry have settled out during transit and have accumulated in a following slug of slurry to form a dilute slug of slurry followed immediately by a concentrated slug of slurry of substantial length, comprising:

placing a premixed slug of slurry of uniform concentration in an upstream end of said pipeline and causing said slurry to flow through the pipeline, providing a sensing means in the pipeline at a location spaced from the upstream end of the pipeline a substantial distance such that a concentrated slug of slurry normally forms to a length requiring approximately one hour pumping time to pass the concentrated slug, I providing a slurry remixing means in the pipeline at a'location spaced downstream of the sensing means and having a slurry storing capacity substantially equal to the dilute slug of slurry and the concen' trated slug of slurry, which slugs together are substantially equal to two hours flow of slurry in' the pipeline,

measuring the concentration of slurry flowing in'the pipeline at said sensing means to detect the presence of a concentrated slug,

initiating operation of the remixing means when a concentrated slug is detected to divert both the dilute slug of slurry and the concentrated slug of slurry into the remixing means,

mixing the dilute slug of slurry and concentrated slug of slurry together to eliminate said concentrated slug and form a slug of slurry of uniform concentration,

reintroducing the remixed slug of slurry into the pipeline,

and causing said remixed slug of slurry to continue to flow through said pipeline.

2. The method as in claim 1, comprising placing said sensing means in the pipeline at a point spaced approximately 250 miles from the upstream end of the pipeline, and providing a plurality of spaced apart pumping stations, in said pipeline to pump said slurry therethrough, said sensing means being provided at one pumping station and initiating operation of the remixing means at the next succeeding pumping station.

3. The method as in claim 2, including the step of pumping water into the pipeline at the remixing means when the slugs of dilute slurry and concentrated slurry are diverted therefrom, to maintain the continuous flow of slurry present in the pipeline beyond the remixing means. 

1. A method of operating a piepline to convey a slurry of comminuted solids in liquid and to remix slugs of slurry flowing through the pipeline in which heavier particles in a slug of slurry have settled out during transit and have accumulated in a following slug of slurry to form a dilute slug of slurry followed immediately by a concentrated slug of slurry of substantial length, comprising: placing a premixed slug of slurry of uniform concentration in an upstream end of said pipeline and causing said slurry to flow through the pipeline, providing a sensing means in the pipeline at a location spaced from the upstream end of the pipeline a substantial distance such that a concentrated slug of slurry normally forms to a length requiring approximately one hour pumping time to pass the concentrated slug, providing a slurry remixing means in the pipeline at a location spaced downstream of the sensing means and having a slurry storing capacity substantially equal to the dilute slug of slurry and the concentrated slug of slurry, which slugs together are substantially equal to two hours flow of slurry in the pipeline, measuring the concentration of slurry flowing in the pipeline at said sensing means to detect the presence of a concentrated slug, initiating operation of the remixing means when a concentrated slug is detected to divert both the dilute slug of slurry and the concentrated slug of slurry into the remixing means, mixing the dilute slug of slurry and concentrated slug of slurry together to eliminate said concentrated slug and form a slug of slurry of uniform concentration, reintroducing the remixed slug of slurry into the pipeline, and causing said remixed slug of slurry to continue to flow through said pipeline.
 2. The method as in claim 1, comprising placing said sensing means in the pipeline at a point spaced approximately 250 miles from the upstream end of the pipeline, and providing a plurality of spaced apart pumping stations, in said pipeline to pump said slurry therethrough, said sensing means being provided at one pumping station and initiating operation of the remixing means at the next succeeding pumping station.
 3. The method as in claim 2, including the step of pumping water into the pipeline at the remixing means when the slugs of dilute slurry and concentrated slurry are diverted therefrom, to maintain the continuous flow of slurry present in the pipeline beyond the remixing means. 